Buzz
The concept of controlling the minds of living creatures might seem like pure science fiction, right? Well, for certain creatures, becoming a real-life zombie is an everyday occurrence. Here are 10 fascinating examples of parasitic behavior manipulation, presented in no specific order.
10. Phorid Flies - Pseudacteon
The Pseudacteon genus, which includes 110 known species, targets ants in South America as a parasitoid. These flies reproduce by laying their eggs inside the ant's thorax. The larvae migrate to the ant’s head and begin feeding on its hemolymph, muscle, and nervous tissues. Over time, the larvae consume the ant's brain, causing it to wander aimlessly for around two weeks. Eventually, the larvae release an enzyme that dissolves the membrane securing the ant's head to its body, leading to its detachment. The fly pupates within the detached head.
9. Toxoplasma Gondii
Toxoplasma gondii is a widespread parasite with cats as its primary host, though it can also be carried by all known mammals, including humans. This parasite can manipulate the behavior of rats and mice, making them attracted to the scent of cats instead of being afraid of it. This change benefits the parasite, as it can reproduce sexually if its infected host is consumed by a cat. The infection is highly targeted, affecting only the rat's fear of cats, while leaving other fears, like fear of open spaces or unfamiliar food smells, unaffected.
8. Euhaplorchis Californiensis
This parasite resides in the digestive system of shorebirds, releasing eggs in the bird's stool that spread across the saltwater marshes and ponds of southern California. Some of these eggs are ingested by snails, where they hatch into larvae. When mature, these larvae leave the snail and swim out into the marsh, eventually infecting a killifish by entering through its gills and traveling along a nerve to the brain. Once in the brain, the parasite induces the fish to swim erratically, making it display its silvery underside in circles near the surface, attracting the attention of birds. This behavior makes the infected fish 30 times more likely to be caught and eaten by a bird. When consumed, the parasite returns to the bird's gut, continuing the cycle.
7. Jewel Wasp - Ampulex Compressa
When a female jewel wasp is ready to lay her egg, she finds a cockroach and delivers two stings. The first paralyzes the roach's front legs, temporarily disabling its ability to move. The second sting is directed straight into the roach's brain, rendering it unable to escape. With the roach no longer capable of resisting, the wasp, much smaller than the cockroach, leads it by grabbing one of its antennae, much like walking a dog on a leash. The wasp then takes her captive back to her nest, lays an egg on its belly, and seals it inside. The larva hatches and feeds on the still-living roach, which lies motionless until it perishes.
6. Hairworm - Spinochordodes Tellinii
The larva of the hairworm parasite develops inside orthopteran insects, such as grasshoppers and crickets. As the worm grows, it consumes the host's internal organs, leaving only the head, legs, and outer shell. Once fully grown—often several times larger than its host—the worm compels the insect to seek out a large body of water and dive in. After entering the water, the worm emerges from its host and swims away to continue its life, while the insect succumbs to drowning.
5. Costa Rican Parasitoid Wasp - Hymenoepimecis Argyraphaga
Hymenoepimecis argyraphaga is a parasitoid wasp found in Costa Rica, with its host being the spider Plesiometa argyra. The adult female wasp paralyzes the spider temporarily and deposits an egg on its abdomen. The egg hatches into a larva that feeds on the spider's blood through small punctures, while the spider continues its normal activities, such as building webs and capturing insects, for one to two weeks. When the larva is ready to pupate, it injects a chemical into the spider that forces it to construct a web unlike any it has built before, and sit still in the center of this web. Even if the larva is removed before the web-building begins, the spider still engages in abnormal web-making. The larva molts, poisons the spider, drains its fluids, and discards the body before spinning a cocoon in the center of the spider's freshly created web. The larva then pupates inside the cocoon and eventually emerges to mate, beginning the cycle once again.
4. Cordyceps Unilateralis
Cordyceps unilateralis is an entomopathogenic fungus that infects ants and manipulates their behavior to ensure the fungus’s spores are widely spread. The spores enter the ant’s body through its spiracles, consuming non-essential soft tissues. When ready to release its spores, the fungus spreads its mycelia into the ant's brain, altering its response to pheromones. This leads the ant to climb to the top of a plant and bite down on a stem with its mandibles, where it remains until death. The fungus kills the ant, and its fruiting bodies grow from the ant’s head, erupting to release spores into the environment.
3. Sacculina
Sacculina is a type of barnacle that parasitizes crabs. Upon encountering a host crab, the female Sacculina larva begins walking over its body until it finds a joint. It then molts, injecting its soft, shell-less body into the crab. Inside the crab, the Sacculina grows, forming a sac on the underside of the crab’s rear thorax, where the eggs would typically be incubated. When the female Sacculina infects a male crab, it disrupts the crab’s hormonal system, sterilizing it and transforming its body to resemble a female’s, including broadening and flattening its abdomen. This transformation even causes the male crab to perform mating behaviors typical of females. The male Sacculina searches for a female Sacculina on the crab’s underside, enters it, and fertilizes her eggs. Despite being infertile due to the parasite, the crab, whether male or female, cares for the eggs as though they are its own. The natural hatching process of a crab involves the female grooming her brood pouch and releasing fertilized eggs into the water, which she stirs with her claw to assist the flow. Similarly, when Sacculina’s parasite eggs are ready to hatch, the crab expels them in a large cloud, once again using its claw to stir the water and help spread the larvae.
2. Lancet Liver Fluke Dicrocoelium Dendriticum
Dicrocoelium dendriticum spends its adult life in the liver of its host. After mating, the eggs are passed through the feces. The first intermediate host, a terrestrial snail, ingests the feces and becomes infected with the larval parasites. The larvae (or cercariae) penetrate the snail’s gut wall and migrate to its digestive tract, where they grow into a juvenile form. In an attempt to defend itself, the snail encapsulates the parasites in cysts, which it then excretes onto the grass. The second host, an ant, finds and consumes these cysts, becoming infected with hundreds of juvenile lancet flukes. Most of the parasites encyst in the ant’s body, maturing into metacercariae, while one moves to the ant's sub-esophageal ganglion—a cluster of nerve cells beneath its esophagus. There, the fluke manipulates the ant’s behavior by altering its nerve functions. As dusk approaches and the temperature drops, the infected ant climbs a blade of grass and clamps its mandibles onto the top, remaining there until dawn. The ant then returns to its normal activity, and the process repeats nightly. Eventually, a grazing animal consumes the blade of grass, along with the parasitic ant, allowing the lancet flukes to return to their preferred host.
1. Glyptapanteles
Glyptapanteles is a genus of parasitic wasps native to Central and North America. The female Glyptapanteles lays her eggs, typically around 80 at a time, inside a young caterpillar. Once the larvae hatch, they begin feeding on the tender internal tissues of the caterpillar until they are fully developed. Afterward, they exit the caterpillar’s body, cling to a branch or leaf, and form their cocoons. However, one or two larvae stay inside the caterpillar, manipulating it to assume a position near the cocoons. The caterpillar arches its back and remains still, ceasing to eat or move. If disturbed, the caterpillar thrashes violently, acting as a bodyguard for the pupating larvae. The caterpillar remains in this state until the cocoons hatch, at which point it dies.
+ Leucochloridium Paradoxum
Leucochloridium Paradoxum is a parasitic flatworm that relies on gastropods, such as snails and slugs, as its intermediate hosts. In its larval form, the worm enters the snail’s digestive system, where it develops into a sporocyst. The sporocyst grows into long tubes and forms swollen sacs, known as ‘broodsacs’, filled with dozens or even hundreds of larvae. These broodsacs invade the snail’s tentacles, especially the middle one when possible, causing them to swell and pulsate, resembling a colorful caterpillar or grub. This transformation impairs the snail’s ability to perceive light, making it more vulnerable to predation. Unlike uninfected snails that avoid predators by seeking darkness, infected snails are drawn to exposed areas, where they are more likely to be preyed upon by birds. This behavior constitutes aggressive mimicry, as the parasite uses its resemblance to a potential food source to gain entry into the host's body.
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